[Low dose intrathecal morphine and postoperative pain relief in elderly patients]

Patient (ASA PS I-III, mean age 68 +/- 14 yr) who had undergone lower extremity surgery under spinal anesthesia were studied to determine the effect of intrathecal administration of morphine 0.1 mg on intra- and postoperative pain relief and its side effects. They were randomly divided into control (C) and intrathecal morphine (M) groups (n = 25, respectively) and received 10 mg tetracaine in 4 ml of a quarter saline with 7.5 micrograms epinephrine. Incidence of intraoperative tourniquet pain was significantly lower in M group (36.8%) than in C group (64.3%). Postoperative pain was examined in terms of the duration until the first supplemental analgesic within 24 hr. The mean duration was 7.0 +/- 4.3 hr in the control group, but 11 patients in the M group needed it within 24 hr (18.1 +/- 6.8 hr, excluding 6 patients who did not receive analgesic). Although incidences of postoperative nausea, vomiting, and itching were higher in M group than in C group, none required antiemetic or naloxone. Both groups showed no difference in postoperative respiratory depression measured by apnea monitor (Eden Trace II, Mallinkrodt Japan, Tokyo). The results suggest that a low dose of intrathecal morphine is effective on postoperative 24 hr pain relief in elderly patients and that its side effects are negligible.